Mercedes reserve driver Pascal Wehrlein posted the quickest lap time on a day of testing affected by rain at the Red Bull Ring.
The morning session was red flagged after just two slow installation laps from McLaren's Stoffel Vandoorne and Ferrari youngster Antonio Fuoco.
Once conditions improved, drivers gradually hit the circuit and the session was extended by two hours to make up for lost time in the morning.
Wehrlein ended with a time of 1:11.005, almost two-tenths of a second quicker than Force India's Esteban Ocon.
Max Verstappen was third for Force India, while Fuoco was fourth but crashed out of running at Turn 1, ending his Formula 1 test debut prematurely.
Romain Grosjean beat compatriot Pierre Gasly, who was testing for Red Bull, to fifth place, while Sauber's Raffaele Marciello was seventh after being delayed by electrical issues.
Vandoorne placed eighth for McLaren, while Susie Wolff completed the runners for Williams as she prepared for her practice outing at the British Grand Prix.